String-Cosmo Day, that took place on the 28th November in APC, Paris.


Dear all,

there has been in recent years a revival of interests in the String Pheno community towards cosmology, either by trying to construct explicit cosmological models for inflation or dark energy/quintessence, or by providing general constraints on such constructions (e.g. via the swampland program). At the same time, cosmologists have launched more and more precise instruments (e.g. Euclid) that will bring new observational constraints on such models. They also face new challenges such as the Hubble tension that bring new input to theorists.

We thought this is a good timing to gather the France-based cosmology and string theory communities, together with few international experts, to foster interactions on targeted topics. To that end, we decided to have a one day workshop,

String-Cosmo Day, that will take place on the 28th November in APC, Paris. This email is an announcement for this event. It is part of the activities of the Transverse Task Forces of the GdR CoPhy. This date is chosen on purpose, since the String Pheno workshop “ Deconstructing the String Landscape” starts the next day in Saclay. It would great to have you participate to this meeting with strings theorists and cosmologists on the 28th November!

Feel free to circulate this information to your group and to whoever might be interested. Registration will open on the 20th September.

All our best wishes

David Andriot, Vivan Poulin, Francesco Nitti

Analogue Cosmology and Gravitation workshop
on the 8th and 9th of november in LKB, Paris


In order to gauge the level of interest in a “Transverse Task Force” of the GDR COPHY, we propose to organize a workshop on the theme of Analogue Gravity and Analogue Cosmology on November 8 and 9, 2023 at the LKB (Jussieu) in Paris. 

Analogue Gravity/Cosmology is an ever-expanding field that is experiencing continued success. Indeed, numerous field theory phenomena have been experimentally observed in the laboratory using analogue systems. We may cite three examples: 

– Surface waves on inhomogeneous flows provide an historic example of an analogue system, in which the Hawking effect, rotational superradiance, and wormhole traversal have been observed in the laboratory. Institut Pprime is currently looking at the black hole laser effect based on their observation of the Hawking effect. Several new devices are being studied to mimic cosmological phenomena, such as the creation of particles during an inflationary phase, or the merging of analogue galaxies. 

– Atomic Bose-Einstein condensates represent another historic platform for Analogue Gravity. The team at Institut d’Optique have used a modulated condensate to mimic and observe certain aspects of preheating physics. Recently, new theoretical developments have accompanied the development of a new experiment which should make it possible to highlight the quantum statistics of the emission in the system. 

– Quantum fluids of light constitute a new platform for the quantum simulation of fields in curved space-time, allowing the observation of quantum statistics of fields in a finely controlled geometry. Two experiments are underway at the Kastler Brossel Laboratory, where black hole geometries of the Kerr and Schwarzschild type are studied and where it was recently shown that it is possible to excite, with vacuum fluctuations, the quasi-normal modes of the quantum field. Attempts to observe this effect are currently underway. 

The task force will strengthen the links between different Analogue Gravity/Cosmology groups by creating a formal discussion forum, and will facilitate the exchange of doctoral students and post-docs, the organization of conferences, the preparation of grant proposals, etc. In addition, the increased proximity with the GDR COPHY theory groups will make it possible i) to bring the tools of relativity to the attention of condensed matter physicists, and ii) to make results of experiments known to the high-energy community. 

The workshop will take place at the Jussieu campus: Sorbonne University, 4 Place Jussieu, 75005 Paris (metro stop “Jussieu”, on lines 7 and 10). Room 13—23.210 (access via the second floor of tower 23). 

Anomalies in cosmology,
November 29th and 30th at LAPTh in Annecy-le-Vieux


You will find more information about the workshop below, 

With the advent of “precision cosmology”, a number of anomalies of diverse statistical significance has emerged. These include, but are not limited to: the “Hubble tension” between measurements of the Hubble parameter with a variety of late-universe probes (cepheid-calibrated supernovae in particular) and its prediction from the LCDM model fit to early-universe data (Planck CMB data in particular); the “S8 tension” between the amplitude of the clustering measured via weak-lensing surveys and that predicted by the Planck/LCDM cosmology; a recent “growth factor” tension which reminds of the S8 tension; as well as older long-standing “cosmic dipole” anomalies, the famous “lithium problem”, and even some intriguing anomalies within Planck data. As of yet, it is not clear whether these anomalies are connected to each other, or even that they are cosmological in origins. The workshop “anomalies in cosmology” aims to gather the efforts of cosmologists interested in these growing (potential) issues of the LCDM model, in order to foster works to better characterize what sorts of systematic effects could be at play, or conversely, what sorts of new physics would be responsible for these anomalies. This will also serve as a platform to discuss with astrophysicists and particle physicists interested in these topics, whose expertise could help the cosmology community in understanding the origin of these anomalies.

Focus of the first workshop:
The workshop “anomalies in cosmology” is organized in the context of the corresponding “transverse task force” of the GDR CoPhy.
The first meeting will take place on November 29th and 30th, and will be hosted by LAPTh, in Annecy-le-Vieux. It will focus on “cepheids”, a key part of the distance ladder. The program includes:
— A review of the Hubble constant measurement by SH0ES
— A review of cepheids for cosmology
— A review of potential systematics with cepheids/SN1a
— Many discussions around the present and future of “cepheid cosmology”
— Hands-on session on data analysis (TBC) 
Invited speakers:
— Richard Anderson (EPFL Lausanne)
— Pierre Kervella (Obs. de Meudon)
— Pierre Astier (LPNHE)

Organizing committee:
Alain Blanchard, Vivian Poulin, Mickaël Rigault, Pasquale Serpico

General MeetingsGeneral Meetings

The first CoPhy GDR General meeting was held
on the 17th. 18th and 19th of January 2023 !
You can find the agenda there: